Photoremovable protecting groups, sometimes called “photocages” or “phototriggers,” are light-sensitive chemical moieties that mask substrates through covalent linkages that render the substrates inert. Upon irradiation, the substrates are released, restoring their reactivity or function. While photocages have important applications in areas such as organic synthesis, photolithography, and light-responsive organic materials, these structures are particularly prized for their ability to trigger biological activity with high spatial and temporal resolution. Examples of such chemical tools include photocaged proteins, nucleotides, ions, neurotransmitters, pharmaceuticals, fluorescent dyes, and small molecules (e.g., caged ATP). These biologically relevant caged molecules and ions can be released from the caging structure within particular biological microenvironments using pulses of focused light. The most popular photocages used in biological studies are the o-nitrobenzyl systems and their derivatives, but other photocages that see significant use include those based on the phenacyl, acridinyl, benzoinyl, coumarinyl, and o-hydroxynaphthyl structures. Unfortunately, a significant limitation of these photocages is that they absorb mostly in the ultraviolet (UV), where the limited penetration of UV light into tissues largely restricts these studies to fixed cells and tissue slices. Furthermore, prolonged exposure of cells or tissues to intense UV light can lead to cellular damage or death. Consequently, new photocaging structures that absorb visible light are needed.